The present invention relates to pellets which disintegrate rapidly in aqueous media and which have sufficient mechanical strength to withstand breakage during manufacture, storage, shipping and handling. More particularly, the invention is directed to multifunctional aids for preparing pellets.
The term xe2x80x9cpelletxe2x80x9d refers to any solid formulation, including but not limited to, tablets, bricks, briquettes, bars, granules, granulates, co-granulates, balls, or blocks. Pellets are well known in the fields of medicine, food science, agriculture, consumer products and more recently they are being used in detergent applications. Pellets offer certain advantages over granular compositions. Pellets are non-dusting, do not require measuring, take up less space because they are compressed and the ingredients that make up a pellet do not separate during transit and storage. Pellets also allow the separation of incompatible ingredients within different layers of the pellet body. Pellets are generally made by compressing or compacting a solid composition which includes one or more active components and various additives or ingredients.
An ongoing problem associated with pellets is the difficulty in providing pellets which have adequate mechanical strength when compacted, yet disintegrate and dissolve quickly when added to an aqueous system. One approach has been to use an additive in preparing a pellet. The problem, however, has proved especially difficult due to the relative rates of dissolution or disintegration of pellets currently in use as compared with granular compositions. Often, it is necessary to compromise between the speed of disintegration of the pellet at the time of use and the strength of handling the pellet before use. In the manufacturing process, a balance must be maintained between a pellet compaction pressure which is, on the one hand, high enough to ensure that the pellets are well formed and do not fracture and/or crumble during transport and storage, and a pellet compaction pressure which is, on the other hand, low enough to achieve an appropriate solubility/disintegration profile. A single material or pellet aid that can be added to ingredients that constitute a pellet would be of significant utility, particularly if the pellet aid possessed a variety of useful functions, in other words a multifunctional pellet aid. The term multifunctional in the present invention refers to a granulated, polymeric pelleting aid which functions for example as a binder, a disintegrating agent and a wicking agent in one solid material.
U.S. Pat. No. 5,916,866 discloses a process for making compacted detergent tablets comprising spraying a coating of a water-soluble organic polymer binder onto the exterior of particles of detergent compositions including a detergent actives and detergent builders. European publication EP 0 896 052 A1 discloses detergent tablets with improved handling strength and swift dissolution which comprise a non-gelling binder and a coating. Examples of non-gelling binders are taken from the prior art but suitable coating materials are dicarboxylic acids for example selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid and mixtures thereof U.S. Pat. No. 5,883,061 teaches polymeric tablet binders which comprise (meth)acrylic acid, maleic anhydride, alkyl (meth)acrylates, alkylhydroxy (meth)acrylates or styrene monomers in polymerised form. The polymeric binders have a Tg ranging from +40 to +120xc2x0 C. and a molecular weight of from 10,000 to 120,000. U.S. Pat. No. 5,360,567 discloses a detergent tablet coated with a polymeric binder, namely polyethylene glycol, which is also capable of acting as a disintegrant by disrupting the structure of the tablet when the tablet is immersed in water. The ""567 patent, however, teaches that it is highly advantageous for the binder/disintegrant to coat or envelop the detergent matrix particles rather than to be simply mixed with them. Clearly, alternative pellet aids are still sought, pellet aids which have more than one type of functionality and which provide pellets having improvements in tablet strength and the rate of disintegration in aqueous media. A single, multifunctional material that can aid in the production of a compacted pellet, a pellet which disintegrates rapidly in aqueous media and which has sufficient mechanical strength to withstand breakage during storage, shipping and handling, would be of substantial utility.
The inventors have discovered a granulated, polymeric pelleting aid which surprisingly functions as a binder, a disintegrating agent and a wicking agent in one solid material. The present invention provides novel pellet aids in the form of granulated compositions used in the processing of pellets by direct compression. Pellets processed with such solid compositions have sufficient mechanical strength to be handled and stored without breakage, yet dissolve rapidly upon contact with water. The pellet aid can be incorporated at any stage of the pelleting process prior to pellet compaction and, optionally the pellet aid can be co-granulated with other functional additives.
In a first aspect of the present invention, there is provided a granulated composition as a pellet aid for binding one or more ingredients and then compacted into a pellet, the pellet having sufficient mechanical strength and rapidly disintegrating when contacted with an aqueous system, the composition including: (a) 20 to 80% by weight of one or more binders, wherein at least one binder is a solution, suspension or emulsion polymer having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C.; (b) 0 to 40% by weight of one or more inorganic solids; and (c) 10 to 80% by weight of one or more organic solids, wherein the granulated composition is present in an amount from 0.25 to 5% by weight of the total weight of the pellet, the granules having a particle size ranging from 100 xcexcm to 3000 xcexcm.
In a second aspect of the present invention, there is provided a process for preparing a multifunctional pellet aid which includes the steps of: (a) premixing 0 to 40% by weight of one or more inorganic solids and 10 to 80% by weight of one or more organic solids; (b) spraying 20 to 80% by weight of one or more solution, suspension or emulsion polymers having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C. on to the premixed solids to achieve a particle size ranging from 100 xcexcm to 3000 xcexcm.
In a third aspect of the present invention, there is provided a process for preparing a multifunctional pellet aid which includes the steps of: (a) preparing a slurry of 0 to 40% by weight of one or more inorganic solids and 20 to 80% by weight of one or more solution, suspension or emulsion polymers having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C.; and (b) spraying the slurry on to 10 to 80% by weight of one or more organic solids to achieve a particle size ranging from 100 xcexcm to 3000 xcexcm.
In a fourth aspect of the present invention, there is provided a process for preparing a solid pellet having high mechanical strength, which can withstand storage and handling without fracturing, and which rapidly disintegrates upon contact with an aqueous system comprising the steps of: (a) mixing 90 to 99.75% by weight of a plurality of ingredients and 0.25 to 10% by weight of a granulated, multifunctional pellet aid composition, wherein the pellet aid comprises (i) 20 to 80% by weight of one or more binders, wherein at least one binder is a solution, suspension or emulsion polymer having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C.; (ii) 0 to 40 % by weight of one or more inorganic solids; and (iii) 10 to 40% by weight of one or more organic solids, the particle size of pellet aid ranging from 100 xcexcm to 3000 xcexcm; (b) compacting the mixture of ingredients and pellet aid to form a pellet.
The solid pellet aid composition usefully employed in accordance with the present invention includes one or more polymeric binders, one or more inorganic solids and one or more organic solids. Suitable binders that make up the pelleting aid include for example acrylic based solution, suspension or emulsion polymers; saccharides such as dextrose, glucose, sucrose, maltose, fructose, cyclodextrin and cyclodextrin derivatives; polysaccharides such as starch, starch derivatives, cellulose, cellulose derivatives such as sodium carboxymethylcellulose, cellulose ethers, methyl cellulose, ethyl hydroxyethyl cellulose, cross-linked cellulose derivatives; naturally occurring gums such as tragacanth gum and gum arabic. Suitable inorganic solids that make up the pellet aid include for example zeolites; clays; alkali- or alkaline-earth metal silicates, such as aluminosilcates; silica; alkali- and alkaline-earth metal carbonates, such as sodium carbonate and magnesium carbonate; alkali- and alkaline-earth metal citrates, such as sodium citrate and calcium citrate; alkali- and alkaline-earth metal acetates, such as sodium acetate. Suitable organic solids that make up the pellet aid include for example polymer dispersants such as poly(meth)acrylic; saccharides such as dextrose, glucose, sucrose, maltose, fructose, cyclodextrin and cyclodextrin derivatives; polysaccharides such as starch, starch derivatives, cellulose, cellulose derivatives such as sodium carboxymethylcellulose, cellulose ethers, methyl cellulose, ethyl hydroxyethyl cellulose, cross-linked cellulose derivatives.
The polymers usefully employed in accordance with the present invention may be soluble or insoluble in water; those which are water insoluble are preferably readily dispersible in water. As used herein, the term xe2x80x9cwater solublexe2x80x9d, as applied to monomers, indicates that the monomer has a solubility of at least 1 gram per 100 grams of water, preferably at least 10 grams per 100 grams of water and more preferably at least about 50 grams per 100 grams of water. The term xe2x80x9cwater insolublexe2x80x9d, as applied to monomers, refers to monoethylenically unsaturated monomers which have low or very low water solubility under the conditions of emulsion polymerization, as described in U.S. Pat. No. 5,521,266. An aqueous system refers to any solution containing water.
Suitable solution, suspension or emulsion polymers usefully employed in accordance with the present invention are prepared from one or more of the following monomers: (meth)acrylic acid, (meth) acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, and (meth)acrylate esters of alkylene glycols, polyalkylene glycols and (C1-C30) alkyl substituted polyalkylene glycols including esters of the formula CH2xe2x95x90CR1xe2x80x94COxe2x80x94O(CH2CHR3O)m(CH2CH2CHR3O)nR2 where R1=H or methyl; R2=H or C1-C30 alkyl; R3=H or C1-C12 alkyl, m=O-40, n=O-40, and m+n is xe2x89xa71, such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate; C1-C30 alkyl-substituted acrylamides; vinyl sulfonate, acrylamido propane sulfonate; dimethyl amino propyl (meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinyl pyrollidone, allyl containing monomers; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing aceto acetoxy functional groups such as aceto acetoxy ethyl methacrylate; vinyl esters of saturated carboxylic acid, e.g., acetate, propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethyl amino ethyl methacrylate; or combinations thereof. Additionally, cross-linking and grafting monomers such as 1,4-butyleneglycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, diallyl phthalate, divinyl benzene, or combinations thereof may be used. As used herein, by xe2x80x9c(meth) acrylatexe2x80x9d or xe2x80x9c(meth)acrylicxe2x80x9d, we mean either acrylate or methacrylate for xe2x80x9c(meth) acrylatexe2x80x9d and acrylic or methacrylic for xe2x80x9c(meth)acrylicxe2x80x9d.
The polymers used in the present invention may be made using known techniques, for example, solution, emulsion or suspension polymerization. Alternatively, a multiphase polymer dissolved or dispersed in water may also be used. By xe2x80x9cmulti-phasexe2x80x9d polymer we mean polymer particles with at least one inner phase or xe2x80x9ccorexe2x80x9d phase and at least one outer or xe2x80x9cshellxe2x80x9d phase. The phases of the polymers are incompatible. By xe2x80x9cincompatiblexe2x80x9d we mean that the inner and the outer phases are distinguishable using techniques known to those skilled in the art. For example, the use of scanning electron microscopy and staining techniques to emphasize differences in the phases is such a technique. The morphological configuration of the phases of the polymers may be for example, core/shell; core/shell particles with shell phases incompletely encapsulating the core; core/shell with a multiplicity of cores; or interpenetrating network particles or phases that contain a multiplicity of hard and soft phases. The first phase may comprise a xe2x80x9csoftxe2x80x9d polymer with a Tg in the range xe2x88x9220 to +95xc2x0 C., preferably a Tg in the range from xe2x88x921 to +95xc2x0 C. Such inner phase polymers may comprise polymerized residues of one or more of the following monomers: (meth)acrylic acid, (meth) acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-30 ethylhexyl (meth) acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; (meth) acrylate esters, for example, where the ester group is a polyalkylene oxide or a C1-C30 alkoxyl polyalkylene oxide; C1-C30 alkyl substituted acrylamides; vinyl sulfonate, acrylamido propane sulfonate; dimethylamino propyl(meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinylpyrollidone, allyl containing monomers; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing aceto acetoxy functional groups such as aceto acetoxy ethyl methacrylate; vinyl esters of saturated carboxylic acid, e.g., acetate; propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethylamino ethyl methacrylate. Additionally, crosslinking and grafting monomers such as 1,4-butyleneglycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, diallyl phthalate, divinyl benzene, or combinations thereof may be used.
The outer phase (sometimes regarded as a xe2x80x9cshellxe2x80x9d if it encapsulates the inner phase), of the multi-phase polymer may comprise either:
i) a polymer with a relatively high Tg value, for example from +40 to 160xc2x0 C., which makes the outer phase relatively hard. The outer phase may comprise polymerized residues of one or more of the following monomers: (meth)acrylic acid, (meth) acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate iso-butyl (meth)acrylate or t-butyl(meth)acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth)acrylate iso-bornyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate; (meth) acrylate esters, for example, where the ester group is a polyalkylene oxide or a C1-C30 alkoxyl polyalkylene oxide; C1-C30 alkyl substituted acrylamides; vinyl sulfonate, acrylamido propane sulfonate; dimethylamino propyl(meth)acrylamide, alkyl vinyl ethers, vinyl chloride, vinylidene chloride, N-vinyl pyrollidone, allyl containing monomers, sulfonates; aromatic vinyl compounds such as styrene, substituted styrenes; butadiene; acrylonitrile; monomers containing aceto acetoxy functional groups such as aceto acetoxy ethyl methacrylate; vinyl esters of saturated carboxylic, e.g. acetate, propionate, neodecanoate; acid or base containing monomers such as, for example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, N,N-dimethylamino ethyl methacrylate; or
ii) a polymer with a high acid content, for example, a polymer with from 10 to 60% by weight of the polymer of for example, (meth)acrylic acid, preferably from 10 to 50% methacrylic acid and with a Tg in the range from xe2x88x9230 to  greater than 100xc2x0 C. In some cases, this can give a relatively soft outer phase and is not strictly thought of as a xe2x80x9cshellxe2x80x9d. Suitable outer phase polymers of this type are described in EP 0 576 128 A; and U.S. Pat. No. 4,916,171.
iii) polyvinyl alcohol. This alcohol when used as an outer layer is found to stabilize various copolymers with Tg""s in the range from xe2x88x9220 to +95xc2x0 C., for example, vinyl acetate homopolymer; vinyl acetate/ethylene copolymer; vinyl acetate/ethylene/acrylic acid or ester copolymer; vinyl acetate/acrylic acid or ester copolymer such as but not limited to those disclosed in U.S. Pat. Nos. 4,921,898 and 3,827,996.
The emulsion polymer has an average particle diameter from 20 to 1000 nanometers, preferably from 70 to 300 nanometers. Particle sizes herein are those determined using a Brookhaven Model BI-90 particle sizer manufactured by Brookhaven Instruments Corporation, Holtsville N.Y., reported as xe2x80x9ceffective diameterxe2x80x9d. Also contemplated are multi-modal particle size emulsion polymers wherein two or more distinct particle sizes or very broad distributions are provided as is taught in U.S. Pat. Nos. 5,340,858; 5,350,787; 5,352,720; 4,539,361; and 4,456,726.
As used herein, the term xe2x80x9csequentially emulsion polymerizedxe2x80x9d or xe2x80x9csequentially emulsion producedxe2x80x9d refers to polymers (including homopolymers and copolymers) which are prepared in aqueous medium by an emulsion polymerization process in the presence of the dispersed polymer particles of a previously formed emulsion polymer such that the previously formed emulsion polymers are increased in size by deposition thereon of emulsion polymerized product of one or more successive monomer charges introduced into the medium containing the dispersed particles of the pre-formed emulsion polymer.
In the sequential emulsion polymerization of the multistage emulsion polymer, the term xe2x80x9cseedxe2x80x9d polymer is used to refer to an aqueous emulsion polymer dispersion which may be the initially-formed dispersion, that is, the product of a single stage of emulsion polymerization or it may be the emulsion polymer dispersion obtained at the end of any subsequent stage except the final stage of the sequential polymerization.
The glass transition temperature (xe2x80x9cTgxe2x80x9d) of the emulsion polymer is typically from xe2x88x9260xc2x0 C. to 100xc2x0 C., preferably from xe2x88x9220 C. to 50xc2x0 C., the monomers and amounts of the monomers selected to achieve the desired polymer Tg range are well known in the art. Tgs used herein are those calculated by using the Fox equation (T. G. Fox, Bull. Am. Physics Soc., Volume 1, Issue No. 3, page 123(1956)). that is, for calculating the Tg of a copolymer of monomers M1 and M2,
1/Tg(calc.)=w(M1)/Tg(M1)+w(M2)/Tg(M2)
wherein
Tg(calc.) is the glass transition temperature calculated for the copolymer
w(M1) is the weight fraction of monomer M1 in the copolymer
w(M2) is the weight fraction of monomer M2 in the copolymer
Tg(M1) is the glass transition temperature of the homopolymer of M1
Tg(M2) is the glass transition temperature of the homopolymer of M2, all temperatures being in xc2x0K.
The glass transition temperatures of homopolymers may be found, for example, in xe2x80x9cPolymer Handbookxe2x80x9d, edited by J. Brandrup and E. H. Immergut, Interscience Publishers.
By xe2x80x9cactive ingredientxe2x80x9d we mean any material which promotes utility and function of a pellet containing such an active ingredient in a particular application or process. The active ingredient may include for example, a material which has activity as a pharmaceutical, an agrochemical, a water treatment agent, a water softening agent, a fabric softening agent, a laundry detergent, a hard surface cleaner, a surface polishing agent, a polish stripping material, a biocide, a stone washing agent or a drain pipe cleaner.
It is believed that the pellet aid alone or in co-granulated form creates an adhesive bond between the active ingredient granules within the pellet composition under the conditions of tablet manufacture, which helps to maintain the integrity of the pellet from the point of manufacture, through storage, until used by the customer.
One embodiment of the present invention is pellets which, in addition to the multifunctional pellet aid, contain active ingredients which have activity as a laundry or dish-washing detergent and/or a hard surface cleaner, referred to collectively as detergent-active compounds. The total amount of additive may be from 0.1 to 25% by weight of the pellet, preferably from 0.5 to 15% and most preferably from 0.5 to 5% by weight of the pellet. Such pellets will typically also contain one or more other ingredients which include builders, suitably in an amount of from 5 to 80 wt %, preferably from 20 to 80 wt %; bleaching agents; processing additives; adjuvants; enzymes; scale inhibitors; emulsifiers; surfactants; soaps; dispersants; zeolites; de-greasing agents; anti-foaming agents; phosphates; phosphonates; optical brighteners; fillers; extenders; soil removers; deflocculating agents; anti-coagulants; anti-drift agents; disintegration agents, including for example, water swellable polymers; water-absorbent polymers; water entraining agents, such as, cellulose; plasticizers or coalescing agents, for example, alkylene glycol alkyl ethers, aromatic glycol ethers, alkyl polyglucosides, polysiloxanes, alcohols and alkyl ester acetates; diluents and carriers. Some of the above-mentioned ingredients may also be applicable for use in non-detergent embodiments of pellets.
The pellet aid is incorporated within the body of the pellets of the invention by any suitable method. A preferred method consists of mixing together a dry mixture of the pellet ingredients including one or more pellet aids and then compacting the mixture in a pelletizing machine to form pellets.
Typical compaction loads for commercial pellets without the binders of the present invention can be up to 5000 pounds. The additives of the present invention allow the same pellet formulation to be formed using lower compaction loads. The actual compaction load required will vary depending on the size of the particles, and the composition of the ingredients that constitute the pellet.
It is known from the disclosure of U.S. Pat. No. 5,360,567 that tablets coated with a polymeric binder, namely polyethylene glycol, are also capable of acting as a disintegrant by disrupting the structure of the tablet when the tablet is immersed in water. The prior art of record further teaches that it is highly advantageous for the binder/disintegrant to coat or envelop the detergent matrix particles rather than to be simply mixed with them. The inventors have discovered, surprisingly, that by intentionally preparing a granulated, polymeric pellet aid having granules particle sizes comparable to the active ingredients and fillers that make up a pellet afford a simple and more efficient approach and yields a composition of significant utility.
Granulation is the process of enlarging the size of a particulate composition, whereby small particles are gathered together into larger, permanent, particular aggregates to render them into free-flow particles. The granulation of the pellet aid, as usefully employed in accordance with the present invention, offers the advantages of a) rendering the pellet aid free flowing; b) densifying the pellet aid; c) reducing the problem of dusting of the pellet aid; and more importantly, d) allowing a process for the manufacture of multifunctional pellet aids.
In a second aspect of the present invention, there is provided a process for preparing a multifunctional pellet aid composition including the steps of premixing 0 to 40 % by weight of one or more inorganic solids and 10 to 40% by weight of one or more organic solids, spraying 20 to 80% by weight of one or more solution, suspension or emulsion polymers having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C. on to the premixed solids to achieve a particle size ranging from 100 xcexcm to 3000 xcexcm.
In one embodiment of the process, it is preferred that inorganic solid is a zeolite or equivalent material, the polymeric material is a copolymer of EHA/MAA or an equivalent solution, suspension or emulsion polymer, and the organic solid is a saccharide such as dextrose. The relative amounts of each respective component, as expressed a weight percent, are preferably 20 to 30%: 20 to 50%: 30 to 50%; more preferably 20:40:40. The preferred particle size of the granulated mixture of components that constitutes the pellet aid ranges from 100 xcexcm to 3000 xcexcm. A more preferred range of particle size that affords higher binding efficiency is from 200 xcexcm to 800 xcexcm. The most preferred particle size of pellet aid granules ranges from 200 xcexcm to 600 xcexcm.
In a third aspect of the present invention, there is provided a process for preparing a multifunctional pellet aid composition including the steps of preparing a slurry of 0 to 40 % by weight of one or more inorganic solids and 20 to 80% by weight of one or more solution, suspension or emulsion polymers having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C. and spraying the slurry on to 10 to 80% by weight of one or more organic solids to achieve a particle size ranging from 100 xcexcm to 3000 xcexcm.
In another embodiment of the process, it is preferred that inorganic solid is a zeolite or equivalent material, the polymeric material is a copolymer of EHA/MAA or an equivalent emulsion polymer, and the organic solid is a saccharide such as dextrose. The relative amounts of each respective component, as expressed a weight percent, are preferably 20 to 30%: 20 to 50%: 30 to 50%; more preferably 20:40:40. The preferred particle size of the granulated mixture of components that constitutes the pellet aid ranges from 100 xcexcm to 3000 xcexcm. A more preferred range of particle size that affords higher binding efficiency is from 200 xcexcm to 800 xcexcm. The most preferred particle size of pellet aid granules ranges from 200 xcexcm to 600 xcexcm.
With respect to the second and third aspects of the invention, in an embodiment related to a manufacturing process, granulated pellet aids with higher binding efficiency are scaled up in a fluidized bed granulation process. The underling principles involved in fluidized beds is the turbulent flow or vortex flow suspension of the solid particles in air. The air lifts and separates the powdered ingredients that constitute the pellet aid. The fluidized bed granulation process combines dry mixing, wet granulation and drying. In order to accommodate liquids or slurries in the granulation process, a spray nozzle is mounted somewhere above the rising fluidized bed of powdered ingredients. Through the nozzle system, a liquid or slurry is added to the fluidized powder to achieve granulation and the desired particle size of the pellet aid granules. It is preferred that the pellet aid granules have a particle size ranging from 100 xcexcm to 3000 xcexcm. A more preferred range of particle size that affords higher binding efficiency is from 200 xcexcm to 800 xcexcm. The most preferred particle size of pellet aid granules ranges from 200 xcexcm to 600 xcexcm.
In a separate embodiment, related to the first three aspects of the present invention, a pellet aid composition is prepared from one or more solution, suspension or emulsion polymers and contains no inorganic solids or organic solids. The polymeric pellet aids may be prepared by freeze-drying or spray-drying. A larger amount, 1 to 2% by weight more, of polymeric pellet aid must be used in making pellets as compared to the granulated, polymeric pellet aid used in making pellets.
In a fourth aspect of the present invention, there is provided a process for preparing a solid pellet having high mechanical strength, which can withstand storage and handling without fracturing, and which rapidly disintegrates upon contact with an aqueous system including the steps of mixing 90 to 99.75% by weight of a plurality of ingredients and 0.25 to 10% by weight of a multifunctional pellet aid, wherein the pellet aid comprises (i) 20 to 80% by weight of one or more binders, wherein at least one binder is a solution, suspension or emulsion polymer having a Tg ranging from xe2x88x9220xc2x0 C. to +95xc2x0 C.; (ii) 0 to 40% by weight of one or more inorganic solids; and (iii) 10 to 40% by weight of one or more organic solids, the particle size of pellet aid ranging from 100 xcexcm to 3000 xcexcm; and compacting the mixture of ingredients and pellet aid to form a pellet.
In one embodiment of this process, it is preferred that plurality of ingredients are used to make a detergent. Typical ingredients that make a detergent can be found in U.S. Pat. Nos. 5,883,061 and 5,360,567, the contents of which is usefully employed in the present invention. The pellet aid is a composition which includes a zeolite or equivalent material, a copolymer of EHA/MAA or an equivalent emulsion polymer, and a saccharide such as dextrose. The relative amounts of each respective component, as expressed a weight percent, are preferably 20:40:40. The amount of pellet aid based on the total weight of ingredients that make up the pellet ranges from 0.25 to 5% by weight, more preferably from 0.5 to 3% and most preferably from 1 to 3%. It is preferred that the pellet aid granules have a particle size ranging from 100 xcexcm to 3000 xcexcm. A more preferred range of particle size that affords higher binding efficiency is from 200 xcexcm to 800 xcexcm. The most preferred particle size of pellet aid granules ranges from 200 xcexcm to 600 xcexcm.
The following examples are presented to illustrate the invention and the results obtained by the test procedures.
Diametral stress fracture, that is, the amount of force applied to the pellet per unit area (KiloPascals, kPa) at the point the pellet fractures, was determined by slowly applying a continuously increasing load to a pellet of known diameter and thickness, until compression failure (fracture). The diametrical fracture stress, X, was calculated according to the equation:
X=2L/d hxcfx80
where L=applied load at point of fracture, d=pellet diameter and h=pellet thickness.
Pellet friability was measured using a friability test device that consisted of a thick glass cylinder, 15 cm in diameter, having three equally spaced glass indentations approximately 2 cm in height. Pellets were placed into the device and tumbled under at a fixed speed. Friability was measured in units of seconds required for the pellet to fracture.
Each pellet (8 g or 40 g) was placed in a metal wire holder and held at the center of a beaker. Four liters of ambient temperature (20-25xc2x0 C.) tap water (150 ppm hardness) was added to the beaker. The water was unstirred (i.e. static) and the time taken for the pellet to disintegrate completely out of the holder was determined.
Dried, polymeric pellets aids at various weight percentages (as indicated in the Tables below) were mixed thoroughly with generic detergent granules and placed inside a stainless steel cylinder (2.8 cm diameter). A piston rod was inserted into the cylinder and the assembly placed between lower and upper plates of a Carver laboratory pellet press. A specified load stress was applied to the pellet at ambient temperature and the pellet was removed from the cylinder. A range of compacting pressures were used and the diametrical fracture stress, friability and pellet disintegration time (determined as described above) were summarized in the Tables below.